Create an access token (one time)
1. On GitHub: Settings → Developer settings → Personal access tokens → Fine-grained tokens → Generate new token.
2. Repository access: Only select repositories → choose the site repository. Permissions → Contents: Read and write.
3. Paste the token here. It is sent only to api.github.com and never stored on any other server.
In test mode you can edit and preview changes on the site in this browser only, without publishing.